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Scientific originality of the project
Over the last 20 years, some 150 molecules have been
detected in interstellar space. These range from simple diatomics
such as molecular hydrogen and carbon monoxide to very complex
species such as large carbon chains containing up to 11 carbon
atoms and Polycyclic Aromatic Hydrocarbon molecules with
typically 50 C-atoms. In the coming decade, the new
European/US observatories coming on line will increase this
inventory of the molecular universe by orders of magnitude.
Identification of the detected lines with specific molecular
species, their analysis in terms of the physical conditions in
the regions, and the implications of these data for the phyiscal
and chemical processes ruling the universe require a close
synergy between laboratory spectroscopists, molecular
physicists, chemists, and astronomers. This requires a new and
innovative approach to this field and that is precisely the scope
of this network. This network will, for the
first time, enlist scientists in all of these
areas to work together towards this common goal: Charting the
molecular universe.
The identification of
specific species in space requires direct comparison of the
particular frequencies of emission or absorption lines observed in
interstellar space with spectroscopic measurements of known
species in a controlled laboratory experiment. In order to
interpret the measured laboratory spectra in terms of the
properties of the molecule (ie., assign lines to specific
transitions), supporting molecular physics quantum chemical
calculations are required. The intensities of lines observed in
space depend directly on the collisional excitation
rates of the molecules with the predominant collision partners,
atomic or molecular hydrogen and helium. These rates will have to
be calculated using quantum chemical methods or measured in the
laboratory by molecular physicists. Such rates can then be used
by astronomers to determine the physical conditions and the
abundances of the molecules involved in the interstellar regions
where the emission or absorption arises. The abundances of
interstellar molecules are the result of a balance between
formation and destruction reactions. The rate coefficients and
products of relevant reactions will have to be measured under
astrophysically relevant conditions (eg., low temperature, low
pressure) or quantum chemically calculated. These rates can then
be used by astronomical modelers to calculate the abundances of
interstellar species. For example, when specific reaction routes
have been proposed and the relevant reaction rate coefficients
measured, abundances of new species can be predicted.
Laboratory spectroscopists can then measure their transition
frequencies while molecular physicists can calculate their
excitation rate coefficients. All of these data together can then
be used by astronomical modelers to predict the expected line
intensities of new species which can then be targeted in
specific searches. It is clear that action in all of these
four science areas has to be strongly interwoven in studies of
the molecular universe.
In our workplan, we have identified 6 key topics in the areas of
molecular complexity in space and in chemistry of regions of star
formation: Water in the universe, carbon chemistry, deuterium:
coming in from the cold, ionization along the star formation
trail, nitrogen chemistry as tracers of protostellar
condensations, and molecular tracers of shocks. In each of these
topics, we expect that our highly interdisciplinary network can
make major breakthroughs thanks to its unique collaborative
framework.